Centrifugal Pump

ABSTRACT

The invention relates to a centrifugal pump ( 10 ) for liquids, comprising a pump spiral housing ( 12 ) and a pump wheel ( 28 ), which is driven by an integrated electromotor ( 14, 20, 34, 36 ), whereby the rotational axis thereof ( 29 ) is arranged in a coaxial in relation to the rotational axis ( 37 ) of the pump wheel ( 28 ). The pump spiral housing ( 12 ) is sealed by a sealing ring ( 72 ) and is connected to the motor housing by means of a bayonet catch ( 74, 78 ) and covers the front side thereof. According to the invention, the motor housing ( 14 ) is pot-shaped and is made of plastic and the base thereof ( 13 ) which is oriented towards the pump spiral housing ( 12 ) forms a common housing wall in relation to the pump spiral housing ( 12 ).

BACKGROUND OF THE INVENTION

The invention relates to a centrifugal pump.

DE 102 04 459 A1 discloses a pump for liquids, in particular a water pump. It is embodied as a centrifugal pump, a pump spiral housing enclosing a pump impeller, which is driven by an electric motor. The latter is arranged coaxially with the pump impeller and has a housing, which is open towards the pump spiral housing. The pump spiral housing is divided in a transverse plane to the axis of rotation of the pump impeller, one half of the pressure spiral being arranged in each part and an outer part enclosing the inner part with a cylindrical fit. A groove to accommodate a sealing ring, which in the assembly process is pushed into a cylindrical seat on the motor casing, is formed between an outwardly protruding shoulder on the free end of the inner part and the end face of the outer part. The sealing ring here bears both on the seating face of the motor casing and on the faces of the inner and outer part of the pump spiral housing forming the groove so that, once assembled, both the motor casing and the pump spiral housing are externally sealed. The connection joining the motor casing and the pump spiral housing together is in the manner of a bayonet catch. For this purpose, the outer part of the pump spiral housing, in proximity to the sealing ring, has radially oriented projections, which are spaced around the circumference and which in the assembly process, are inserted axially between corresponding undercuts and come to lie behind undercuts on the motor casing. Turning the pump spiral housing through a predefined angle relative to the motor casing brings the projections behind the undercuts, exerting an axial force on the sealing ring and causing the sealing ring to bear tightly against the adjoining components. A twist lock prevents the connection accidentally coming undone. No additional fasteners are needed for connecting the motor casing to the pump spiral housing and only one single sealing ring is required. This facilitates assembly and dismantling of the pump and minimizes production and repair costs.

SUMMARY OF THE INVENTION

According to the invention the motor casing is of canister-shaped design and is made from plastics, its base facing the pump spiral housing forming a common housing wall with the pump spiral housing. This results in a compact construction with hermetic sealing between the current-carrying areas of the electric motor, that is to say the stator, a printed circuit board and an electronics cover, and the liquid-ducting parts of the pump section. At the same time this reduces the number of parts and facilitates the connection of the motor casing to the spiral housing in the manner of a bayonet catch. With the connection according to the invention, the rotation of the parts relative to one another produces no axial displacement of the parts. The axial marrying up of the parts is accomplished prior to the rotational movement, thereby avoiding tolerance problems.

According to one development of the invention, the base of the motor casing has a protuberance, facing the open end and concentric with the axis of rotation, and having an approximately cylindrical dividing wall and an internal base. In its central area this base has a thickening, in which a bearing axis pointing towards the pump spiral housing is injection molded. A rotor of the electric motor, which usually comprises permanent magnets, is integrally formed with the pump impeller and is rotatably supported on the bearing axis by an injection molded bearing. The rotor and the pump impeller are advantageously secured axially on the bearing axis between the thickening and a mushroom-type stop. The latter is pushed onto the free end of the bearing axis and engages with a twist lock in a recess on the bearing axis. With its external contour the mushroom-type stop projects into an inlet connection on the spiral housing, its contour being designed so that favorable flow conditions are created in the transition from the inlet connection to the pump impeller. Here too, no additional fasteners are needed.

According to one development of the invention a coil shell of the stator of the electric motor is inserted in the annular space between the dividing wall and the outer wall of the motor casing, the coil shell sealing said annular space with one end wall. The coil shell is likewise connected to the motor casing in the manner of a bayonet catch, projections on the circumference of its end wall engaging behind undercuts on the motor casing which are oriented radially inwards. The coil shell here suitably provides external support for the walls of the motor casing subjected to the delivery pressure and by way of its projections transmits the forces to the undercuts on the motor casing, so that the walls of the motor casing in this area can be kept very thin. It also prevents any elongation of the dividing wall. Elongation would result in a shift in the position of the electronics, which are accommodated in that part of the motor casing which towards the free end adjoins the coil shell. The forces transmitted to the coil shell by the inner walls of the motor casing act as tensile forces in the shell and are transmitted to the stable outer wall by the shortest route. In addition, this affords the same advantages in the connection between the coil shell and the motor casing as accrue from the connection between the pump spiral housing and the motor casing. Incorrect assembly is suitably prevented by at least one coding in the area of the undercuts on the motor casing.

In a further development the coil shell, in the area of the annular space in the motor casing, is wound from its end wall to the base of the motor casing with varnished copper wire, the wire ends of which are laid to support points for insulation displacement connectors. A coil formed from the varnished copper wire is arranged in a radially open annular space in the coil shell, via the opening in which a stator ring is pressed onto the coil shell as far as the end wall. The stator ring is in contact with yoke parts, which are injection molded in the coil shell. Advantageously resting on the support points is a printed circuit board, which is held by insulation displacement connectors and the tracks of which are bonded by press-in contacts of the insulation displacement connections. This affords a secure mounting of the bearing plate, which requires no great assembly outlay, since during assembly the bonding ensues automatically from the method of fastening. It is furthermore advisable, in a pocket in the end wall of the coil shell, on the side facing the rotor, to provide a Hall sensor, the pins of which are laid to a support point and are electrically bonded to the insulation displacement connections by pressing the insulation displacement connections into the assigned support point. These connections have press-in contacts, which hold a printed circuit board and accordingly bond the tracks thereof. Connector pins for a connector are prefitted to the printed circuit board.

The motor casing is suitably sealed at the end face by an electronics cover. This has an injection molded seal, through which the connector pins are fed during the assembly process. The electronics cover is likewise assembled without any additional fasteners. For this purpose the electronics cover, on its circumference, has pliable hooked catches, which latch in the recesses in the outer wall of the motor housing during the assembly process. In order to facilitate assembly, pins are molded onto the electronics cover, which engage in pre-centering sleeves in order to center the electronics cover in relation to the coil shell and the printed circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages are set forth in the following description of the drawing. Exemplary embodiments of the invention are represented in the drawing. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will also give appropriate consideration to individual features and will be capable of bringing these together in further suitable combinations.

In the drawing:

FIG. 1 shows a longitudinal section through a centrifugal pump according to the invention,

FIG. 2 shows a perspective longitudinal section through a motor casing,

FIG. 3 shows a perspective view of a coil shell,

FIG. 4 shows an enlarged detail from FIG. 3,

FIG. 5 shows a longitudinal section through a coil shell,

FIG. 6 shows a perspective partial view of a motor casing with a fitted coil shell,

FIG. 7 shows a perspective view of a centrifugal pump with a cutaway motor casing and coil shell and

FIG. 8 shows a perspective view of a centrifugal pump with a fitted printed circuit board.

DETAILED DESCRIPTION

The main integral parts of a centrifugal pump 10 according to the invention are a pump spiral housing 12 with an inlet connection 102 and an outlet connection 104, a pump impeller 28 and an electric motor with a motor casing 14, a stator 34 and a coil shell 40 together with a printed circuit board 94 and an electronics cover 20. The motor casing 14 is made of plastics and is of canister-shaped design. It comprises a base 13, which is open to the pump spiral housing 12 and which forms a common housing wall with the integrally formed pump spiral housing 12. Outwardly adjoining the base 13 is an outer wall 15, whilst in the central area the base 13 has a slight depression, which is formed by an inner base 17 and a dividing wall 19. At its center the inner base 17 has a thickening 18, in which a bearing axis 22 is injection molded. The motor casing 14 is therefore hermetically sealed off from the pump spiral housing 12. By means of an injection molded bearing 30, a rotor 36 is supported on the bearing axis 22 so that it can rotate about an axis of rotation 29. Molded onto the rotor 36 at the end face is the pump impeller 28, which projects axially into the pump spiral housing 12 and through which the flow passes radially from the inlet connection 102 to the outlet connection 104. The axis of rotation of the pump impeller 28 is denoted by 37. The rotor 36 and the pump impeller 28 are axially secured on the bearing axis 22 between the thickening 18 and a mushroom-type stop 24, on which the bearing 30 rises axially. The mushroom-type stop 24 is pushed over the free end of the bearing axis 22 and latched in a recess 32, the mushroom-type stop 24 having a twist lock not represented in further detail. The external contour of the mushroom-type stop 24 facing the inlet connection 102 is designed to produce a favorable incident flow against the pump impeller 28.

The pump spiral housing 12 is connected to the motor casing 14 in the manner of a bayonet catch, by pushing radial projections 74 on the circumference of the motor casing 14 axially through between corresponding undercuts 78 on the pump spiral housing 12 and turning the pump spiral housing 12 through an angle of approximately 150 relative to the motor casing 14, so that the projections 74 come to lie behind the undercuts 78. Prior to the rotational movement an axial force is exerted on a sealing ring 72 in the form of an O-ring arranged between the spiral housing 12 and the base 13 of the motor casing 14. In the limit position, a hooked catch 80 arranged in the peripheral direction on the circumference of the motor casing 14 engages with a stop 82 on the pump spiral housing 12, so that the motor casing 14 is also circumferentially fixed in relation to the pump spiral housing 12.

A coil shell 40 of the stator 34 is inserted into the annular space between the outer wall 15 and the dividing wall 19 of the motor casing 14. It is connected to the motor casing 14 in the manner of a bayonet catch by pushing projections 56 on the circumference of an end wall 41 of the coil shell 40 between corresponding undercuts 62 on the motor casing 14 and turning to the right through approximately 40° so that they come to lie behind the undercuts 62, thereby fixing the stator 34 to the coil shell 40 in the motor casing 14. At least one coding 64, and advantageously three codings, ensure that only one fitting position is possible. In the area of its projection 56 the coil shell 40 has a hooked catch 58, which serves as twist lock and engages in a recess 66 in the motor casing 14 when the coil shell 40 is in the limit position (FIG. 6). In the assembly process, the hooked catch 58 is tensioned by the inside of the outer wall 15 of the motor casing 14 diverging conically outwards.

In order to be able to design the dividing wall 19 and the base 17 of the motor casing 14, which are exposed to the delivery pressure of the centrifugal pump 10, as thin as possible, so as to reduce the distance between the rotor 36 and the stator 34, the coil shell 40 supports this area and by way of its projections 56 transmits the forces to the undercuts 62 of the motor casing 14 as tensile forces by the shortest possible route. The coil shell 40 likewise prevents elongation of the dividing wall 19, which would shift the position of the electronics, especially a printed circuit board 94, in an axial direction.

The coil shell 40, in the area of the annular space between the dividing wall 19 and outer wall 15, is wound between its end wall 41 and the base 13 of the motor casing 14 with a varnished copper wire 52, the ends of which are laid to support points 42, 44, 46 on the side of the end wall 41 of the coil shell 40 facing the electronics cover 20. The coil formed by the varnished copper wire 52 is accommodated in a radially open annular space in the coil shell 40. The annular space is sealed by a stator ring 38, which is pressed onto the coil shell 40 and bonds yoke parts 39, which are injection molded into the coil shell 40 in the area of the coil.

A Hall sensor 98, which is inserted into a pocket 60 in the coil shell 40, is provided on the coil shell 40, its pre-bent pins 54 being laid to a support point 44. The position of the Hall sensor 98 can be secured by a bonding point. The ends of the varnished copper wire 52 and the pins 54 are bonded by insulation displacement connections 48, which are pressed into the associated support points 42, 44. The insulation displacement connection 48, which is assigned to the support point 46, only has retaining functions, in order to fix the printed circuit board 94 to the support points. The insulation displacement connections 48 have press-in contacts 86 at their free ends. The printed circuit board 94 is now pressed onto these and its tracks are bonded. All necessary electrical connections to the electronics are thereby established. Connector pins 88 for the connector are pre-fitted to the printed circuit board 94 by soldering or pressing in.

The electronics cover 20 with a pre-fitted O-ring 96 on its circumference is pushed into the open end of the motor casing 14, the O-ring 96 being compressed by the inside of the outer wall 15 diverging conically outwards. The electronics cover 20 has hooked catches 92 spaced around its circumference, which are radially pliable and engage in recesses 16 in the motor casing 14 when the electronics cover 20 is in the limit position. To facilitate assembly, pins 90 which slide in pre-centering sleeves 50, are molded onto the inside of the electronics cover 20. These sleeves are molded onto the coil shell 40. The electronics cover 20 has openings with an injection molded seal 26, through which the connector pins 88 of the printed circuit board 94 are pushed. In order that the printed circuit board 94 is not thereby subjected to bending stresses, support points 100, on which the printed circuit board 94 rests, are provided on the coil shell 40 in the area of the connector pins 88. In the event of variations in length due to internal pressure or thermal expansion of the components, these can be transmitted to the plug-and-socket connection by displacement of the connector pins 88 through the molded-on seal 26, without any great force being exerted on the electrical connections of the printed circuit board 20. 

1. A centrifugal pump (10) for liquids having a pump spiral housing (12) and a pump impeller (28), which is driven by an integral electric motor (14, 20, 34, 36), the axis of rotation (29) of which is arranged coaxially with the axis of rotation (37) of the pump impeller (28), the pump spiral housing (12) being sealed by a sealing ring (72) and connected to the motor casing (14) means of a bayonet catch (74, 78), covering the end face of the motor casing, characterized in that the motor casing (14) is of canister-shaped design and is made from plastics, its base (13) facing the pump spiral housing (12), forming a common housing wall with the pump spiral housing (12).
 2. The centrifugal pump (10) as claimed in claim 1, characterized in that the base (13) has a protuberance, facing the open end of the motor casing (14) and concentric with the axis of rotation (29), with an approximately cylindrical dividing wall (19) and an internal base (17), which in its central area has a thickening (18), in which a bearing axis (22) pointing towards the pump spiral housing (12) is injection molded, on which a rotor (36) of the electric motor is rotatably supported.
 3. The centrifugal pump (10) as claimed in claim 2, characterized in that the rotor (36) and the pump impeller (28) are integrally formed and are supported by way of an injected-molded bearing (30) on the bearing axis (22).
 4. The centrifugal pump (10) as claimed in claim 3, characterized in that the bearing axis (22), at its free end, carries a mushroom-type stop (24), which axially secures the bearing (30) in that the mushroom-type stop (24) engages by means of a twist lock in a recess (32) in the longitudinal axis (22).
 5. The centrifugal pump (10) as claimed in claim 1, characterized in that a coil shell (40) of a stator (34) of the electric motor is inserted in an annular space between the dividing wall (19) and the outer wall (15) of the motor casing (14) and seals the annular space with one end wall (41).
 6. The centrifugal pump (10) as claimed in claim 5, characterized in that the coil shell (40), in the area of the annular space, is wound from the end wall (41) to the base (13) of the motor casing (14) with varnished copper wire (52), the wire ends of which are laid to support points (42, 44, 46) for insulation displacement connectors (48).
 7. The centrifugal pump (10) as claimed in claim 6, characterized in that a stator ring (38) is pressed over the coil formed from the varnished copper wire (52) onto the coil shell (40) as far as the end wall (41).
 8. The centrifugal pump (10) as claimed in claim 5, characterized in that the end wall (41) has projections (56) on its circumference, which by turning the coil shell (40) relative to the motor casing (14) during the assembly process engage behind inwardly projecting undercuts (62) on the motor casing (14) in the manner of a bayonet catch.
 9. The centrifugal pump (10) as claimed in claim 6, characterized in that at least one coding (64) is provided in the area of the undercuts (62).
 10. The centrifugal pump (10) as claimed in claim 5, characterized in that the support points (42, 44, 46) with insulation displacement connections (48) are arranged on the end wall (41) on the side facing the opening in the motor casing (14), a printed circuit board (94), the tracks of which are bonded by press-in contacts (86) of the insulation displacement connections (48), resting on the support points (42, 44, 46).
 11. The centrifugal pump (10) as claimed in claim 5, characterized in that a Hall sensor (98), the pins (54) of which are electrically bonded to the insulation displacement connections (48) by pressing the insulation displacement connections (48) into the associated support point (44), is inserted into a pocket (60) in the end wall (41) of the motor housing (14) on the side facing the rotor (36).
 12. The centrifugal pump (10) as claimed in claim 5, characterized in that a hooked catch (58), which engages in a recess (66) on the motor casing (14) and circumferentially fixes the coil shell (40) in relation to the motor casing (14), is provided on the circumference of the end wall (41).
 13. The centrifugal pump (10) as claimed in claim 10, characterized in that the hooked catch (58) adjoins a projection (56) of the coil shell (40).
 14. The centrifugal pump (10) as claimed in claim 1, characterized in that the coil shell (40) supports the dividing wall (19) and/or the internal base (17) of the motor housing (14).
 15. The centrifugal pump (10) as claimed in claim 1, characterized in that the opening in the motor housing (14) is sealed by an electronics cover (20), which has axially oriented connector pins (88), which project through an injection molded seal (26) into the motor casing (14) and engage in a power connection (100) of the coil shell (40).
 16. The centrifugal pump (10) as claimed in claim 15, characterized in that axially oriented, inward-pointing pins (90), which engage in pre-centering sleeves (50) provided on the coil shell (40) for pre-centering in relation to the coil shell (40), are molded onto the electronics cover (20).
 17. The centrifugal pump (10) as claimed in claim 15, characterized in that the electronics cover (20), on its circumference, has radially pliable hooked catches (92), which engage in recesses (16) in the motor housing (14).
 18. The centrifugal pump (10) as claimed in claim 15, characterized in that the electronics cover (20), offset axially inwards in relation to the hooked catches (92), has a radially acting sealing ring (96), which bears tightly against the inside of the outer wall (15) of the motor casing (14).
 19. The centrifugal pump (10) as claimed in claim 12, characterized in that the inside of the outer wall (15) diverges conically in relation to the opening in the motor casing (14). 